core: migrate code to benefit from 3.9 stuff (#401)

for now keeping ruff on 3.8 target version, need to sort out modules as well

my/core/utils/concurrent.py

@@ -1,6 +1,7 @@
-import sys
+from __future__ import annotations
+
 from concurrent.futures import Executor, Future
-from typing import Any, Callable, Optional, TypeVar
+from typing import Any, Callable, TypeVar
 
 from ..compat import ParamSpec
 
@@ -15,7 +16,7 @@ class DummyExecutor(Executor):
      but also want to provide an option to run the code serially (e.g. for debugging)
     """
 
-    def __init__(self, max_workers: Optional[int] = 1) -> None:
+    def __init__(self, max_workers: int | None = 1) -> None:
         self._shutdown = False
         self._max_workers = max_workers